Field of the Disclosure
The present disclosure relates to processing hard dielectric materials using lasers, and more particularly, relates to a multi-laser system and method for cutting and post-cut processing hard dielectric materials such as ceramics.
Background Art Discussion
Hard dielectric materials, such as sapphire (Al2O3), toughened glass (e.g., GORILLA® glass), and other ceramics, may be used for many industrial applications such as optical windows, hard materials preventing abrasion, and buffer materials for a semiconductor emitting device, and the like. Conventional mechanical methods for treating or processing sapphire and other such materials include diamond scribing and blade dicing; however, these methods often lead to breaking the substrate, which lowers production yields.
Laser processing methods have been used in an effort to increase efficiency because they provide a noncontact process that is more efficient for high volume production. The laser scribed cutting depth may also be controlled to reduce stress on the wafer during the break process, and laser scribing facilitates precise positioning of scribes. Thus, laser processing has overall advantages of increased throughput, low cost, ease of use, and high yields compared to traditional mechanical methods.
Certain materials, however, present challenges when processing using lasers. The bandgap of sapphire, for example, is approximately 8 eV, and under normal low intensity illumination, sapphire is optically transparent from 5000 nm to about 300 nm. Therefore, conventional laser processing of sapphire has used lasers that are more likely to be absorbed in sapphire, such as DUV and UV lasers operating in a wavelength range between about 157 and about 355 nm.
Laser processing of sapphire has also been performed using ultrafast lasers (e.g., picosecond and shorter pulse widths) and/or Q-switched pulse lasers with nanosecond pulse widths. Such lasers may be used to emit pulses with high peak power capable of ablating sapphire. Picosecond lasers may also be used to focus inside a sapphire substrate forming cracks within the substrate without affecting the top and bottom surfaces. The cut parts may then be mechanically separated from the substrate after the cracks are formed.
The existing techniques used for laser processing of sapphire discussed above also suffer from other drawbacks. In particular, the cost of pulsed lasers is high and the multi-step process of forming cracks and separating parts is time consuming and cost inefficient. Also, the wavelengths used in UV cutting require the use of crystals, which may have a short useful life and may present issues with the maintenance of these lasers.
Cutting hard dielectric materials also presents challenges because of the defects and imperfections that might form in the material after cutting. Hard dielectric materials including crystalline and amorphous ceramics have a tendency to fail in tension before they fail in compression. Stress concentrations at the cut edges, for example, may lead to crack propagation throughout the material. These materials may be more susceptible to these defects and imperfections when certain types of lasers are used to perform the cutting. Sometimes the lasers that perform the cutting most efficiently (e.g., at a lower cost and higher speeds) may cause edge defects such as chipping, cracking, and induced stress concentrations proximate the cut edges.
Accordingly, a need exists for a system and method of efficiently laser cutting hard dielectric materials at increased speeds in a time-effective and a cost-effective manner while also reducing edge defects.